Zhai Suling, Hansen Raino K, Taylor Richard, Skepper Jeremy N, Sanches Raquel, Slater Nigel K H
Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
Biotechnol Prog. 2004 Jul-Aug;20(4):1113-20. doi: 10.1021/bp034362x.
Lyophilization is the most popular method for achieving improved stability of labile biopharmaceuticals, but a significant fraction of product activity can be lost during processing due to stresses that occur in both the freezing and the drying stages. The effect of the freezing rate on the recovery of herpes simplex virus 2 (HSV-2) infectivity in the presence of varying concentrations of cryoprotectant excipients is reported here. The freezing conditions investigated were shelf cooling (223 K), quenching into slush nitrogen (SN2), and plunging into melting propane cooled in liquid nitrogen (LN2). The corresponding freezing rates were measured, and the ice crystal sizes formed within the samples were determined using scanning electron microscopy (SEM). The viral activity assay demonstrated the highest viral titer recovery for nitrogen cooling in the presence of low (0.25% w/v sucrose) excipient concentration. The loss of viral titer in the sample cooled by melting propane was consistently the highest among those results from the alternative cooling methods. However, this loss could be minimized by lyophilization at lower temperature and higher vacuum conditions. We suggest that this is due to a higher ratio of ice recrystallization for the sample cooled by melting propane during warming to the temperature at which freeze-drying was carried out, as smaller ice crystals readily enlarge during warming. Under the same freezing condition, a higher viral titer recovery was obtained with a formulation containing a higher concentration of sugar excipients. The reason was thought to be twofold. First, sugars stabilize membranes and proteins by hydrogen bonding to the polar residues of the biomolecules, working as a water substitute. Second, the concentrated sugar solution lowers the nucleation temperature of the water inside the virus membrane and prevents large ice crystal formation within both the virus and the external medium.
冻干是提高不稳定生物制药稳定性最常用的方法,但由于在冷冻和干燥阶段都会产生应力,在加工过程中会有很大一部分产品活性丧失。本文报道了在不同浓度的冷冻保护剂辅料存在下,冷冻速率对单纯疱疹病毒2(HSV-2)感染性恢复的影响。研究的冷冻条件为搁板冷却(223K)、淬入淤浆氮(SN2)和投入液氮冷却的熔融丙烷(LN2)。测量了相应的冷冻速率,并使用扫描电子显微镜(SEM)确定样品中形成的冰晶大小。病毒活性测定表明,在低(0.25%w/v蔗糖)辅料浓度存在下,氮气冷却的病毒滴度回收率最高。在通过替代冷却方法得到的结果中,经熔融丙烷冷却的样品中病毒滴度的损失始终是最高的。然而,通过在较低温度和较高真空条件下进行冻干,可以将这种损失降至最低。我们认为这是由于在升温至进行冻干的温度时,经熔融丙烷冷却的样品的冰重结晶比例较高,因为较小的冰晶在升温过程中容易变大。在相同的冷冻条件下,含有较高浓度糖类辅料的制剂获得了更高的病毒滴度回收率。原因被认为有两方面。首先,糖类通过与生物分子的极性残基形成氢键来稳定膜和蛋白质,起到水替代物的作用。其次,浓缩的糖溶液降低了病毒膜内水的成核温度,并防止在病毒和外部介质中形成大的冰晶。